Methylcellulose

• BPMethylcellulose
• JPMethylcellulose
• Ph. Eur.Methylcellulose
• USP–NFMethylcellulose

Cellulose methyl ether; methylcellulosum; Benecel; Culminal MC; Methocel A; Metolose SM; E461

Cellulose methyl ether · [9004-67-5]

[C6H7O2(OH)x(OCH3)y]n · ≈ 10 000–220 000

Gelling agent, viscosity modifier, Binder

Typical concentrations: 1–5% binder · Dosage forms: Liquid, Solid

Used in oral and topical products as a viscosity-increasing, suspending, emulsifying and thickening agent, as a tablet binder, coating polymer and disintegrant, in modified-release matrices, and therapeutically as a bulk laxative. Typical concentrations: creams, gels and ointments 1–5%; emulsifying agent 1–5%; ophthalmic preparations 0.5–1%; suspensions 1–2%; tablet binder 1–5%; tablet coating 0.5–5%; tablet disintegrant 2–10%; modified-release matrix 5–75%.

A white to yellowish-white, practically odourless and tasteless, fibrous powder or granules. It is a cellulose in which part of the hydroxyl groups are methylated; grades are distinguished by the viscosity of a 2% w/v aqueous solution.

Methoxy content

26.0–33.0% (degree of substitution about 1.5–2.0)

Viscosity (2% w/v aqueous solution, 20 °C)

grades from about 5 to about 75 000 mPa·s

pH

5.0–8.0 (1% w/v aqueous solution)

Thermal gelation

aqueous solutions gel on heating, at about 50–55 °C, and re-liquefy on cooling

Solubility

swells and disperses in cold water to give a clear to opalescent viscous colloidal solution; practically insoluble in hot water, acetone, ethanol, chloroform and ether

The powder is stable, though slightly hygroscopic. Solutions are stable at pH 3–11 at room temperature; below pH 3 acid hydrolysis lowers viscosity, and heating reduces viscosity reversibly. Solutions are prone to microbial spoilage and need a preservative. Store in a well-closed container in a cool, dry place.

Incompatible with aminacrine hydrochloride, chlorocresol, mercuric chloride, phenol, resorcinol, tannic acid, silver nitrate, cetylpyridinium chloride, p-hydroxybenzoic acid esters and strong oxidising agents. High concentrations of electrolytes salt out the polymer and increase viscosity or cause precipitation.

Made by treating cellulose (wood pulp or cotton linters) with sodium hydroxide and then with methyl chloride; the product is washed with hot water, dried and milled.

Not absorbed after oral administration and regarded as non-toxic and non-irritant. Large oral doses act as a bulk laxative and may cause flatulence; it should be taken with enough fluid to avoid oesophageal or intestinal obstruction.

Observe normal precautions for the quantity handled. Avoid generating dust; eye protection, gloves and a dust mask are recommended.

GRAS listed. Accepted as a food additive in Europe (E461). Included in the FDA Inactive Ingredient Database (nasal, ophthalmic, oral, topical and vaginal preparations) and in non-parenteral medicines licensed in Europe.

Hypromellose; ethylcellulose; hydroxyethyl methylcellulose; hydroxypropyl cellulose; carboxymethylcellulose sodium.

To prepare lump-free solutions, disperse the powder in about a third of the water heated to 80–90 °C, then add the remainder as cold water or ice and stir while cooling. Its thermal gelation can be exploited in in-situ gelling formulations but may cause problems during hot processing.